I think there is an underlying message in both issues: You can't fall too far behind in technology, or the pain will increase incrementally over time. You can't expect that the ongoing technology will be backward compatible forever.

If you're back in OS 9, you have no tech support. Almost no one else is still running the operating system. It could be the PDF, it could be the OS, it could be an InDesign 2 bug. There's no way to tell.

If I had a client who was still using Pagemaker, I'd tell them that I could not help them. I cannot run Pagemaker on my system, and have no way of helping them diagnose a problem. There may be others who are equipped to help them, but happily I am not.